1. Field of the Invention
The present invention relates to a solid-state imaging device such as an area CCD (charge coupled device) image sensor, and a method for driving such a solid-state imaging device.
2. Description of the Prior Art
One type of known solid-state imaging devices comprises full frame transfer vertical shift registers, in which signal charges stored in all light-receiving portions two-dimensionally arranged can be read individually at one time in a vertical direction. This type of solid-state imaging device is advantageous in that the resolution in the vertical direction is improved compared with a general type solid-state imaging device having the same number of light-receiving portions. The vertical direction as referred to in this specification means one of the two dimensional directions, while the other is referred to as the horizontal direction.
In a general type solid-state imaging device applied to a video camera of a standard TV system in which interlaced scanning is normally adopted, signals of two vertically adjacent pixels of different combinations are mixed so as to correspond to the interlaced scanning of the standard TV system. Therefore, the number of pixels in the vertical direction required for the general solid-state imaging device is equal to the total number of scannings in the standard TV system.
On the other hand, in a solid-state imaging device provided with the full frame transfer vertical shift registers, signals of all pixels are read individually in the vertical direction. Therefore, when this type of device is applied to the video camera of the standard TV system, the number of pixels in the vertical direction should be a half of the total number of scannings. As a result, the resolution in the vertical direction is deteriorated compared with a general type solid-state imaging device. When the solid-state imaging device provided with the full frame transfer vertical shift registers has the same number of pixels in the vertical direction as the general type device, the image information read therefrom can not be directly reproduced on a TV screen. In this case, the image information must be first recorded on a recording medium such as a magnetic disk, and then converted into data for TV display so as to be reproduced on a TV screen.
Because of the above-described limitation, the solid-state imaging device provided with the full frame transfer vertical shift registers has been mainly used for a camera for a still image display, for example, and has not been applied to a device such as a video camera for a moving image display.
The objective of the present invention is to provide a solid-state imaging device provided with full frame transfer vertical shift registers, which is capable of effecting a moving image display, in addition to a still image display, when applied to the standard TV system, and a method for driving such a device.